1. Field of the Invention
This invention relates to disk drive suspensions, and more particularly, to disk drive suspensions having the suspension assembly held onto the actuator arm by a planar or nearly planar mount plate and connector combination. The invention combination mount plate and connector does not rely on radial forces to engage the mount plate and arm, as is conventional, but uses axial forces imposed on the opposite sides of the arm and mount plate by flanges carried by the connector.
2. Related Art
Known suspension attachment methods generally involve the use of ball staking or swaging, e.g. as shown in U.S. Pat. No. 4,829,395. These prior art techniques are well adapted to the case where a stack of four or more head gimbal assemblies; (HGAs) is to be assembled. The prior art achieves the reliable attachment and labor efficiency associated with ball staking by incorporating a mount plate that has a boss. The boss is designed so that it can form an attachment to the actuator arm with the use of planar tooling that can be inserted into a stack. Planar tooling holds the pieces together without requiring access to the interior of the boss cylinder.
There is, however, a relentless drive to achieve ever-lower costs for disk drive suspensions. In addition, there is a trend toward the production of disk drives that have reduced number of disks. As the areal density (number of digital bits stored per unit area) increases historically at a compound annual rate of 60%, the disk drives no longer need to have four, six, or more disks per drive to get the total capacity deemed necessary. Industry leaders have announced that they can achieve 20 Gb (Gigabits) per square inch or 2.5 GB (GigaBytes) per square inch, so that a 3.5 inch single disk drive will soon be able to store 20 GB of data, assuming that there are about 8 square inches of surface available on both sides of a 3.5-inch disk.
These trends mean that the best design is one that achieves the lowest cost for a single disk arrangement, with the ability to stack multiple disks being less important than before. The mount plate is a significant cost element at about 4 cents per part or 15 to 25% of the material cost of a suspension without wireless flexure, 10 to 20% of the material cost of a suspension with wireless flexure.
Accordingly, the invention offers the following advantages:
The mount plate design is changed so that it is planar, i.e. has no annular boss, or essentially planar i.e. having a small, even vestigial, boss sized to be useful only for guiding the alignment of the mounting plate and actuator arm opening. In the invention, typically, the boss, if any, is made to be less than half the thickness of the mounting plate flange, instead of one to one and a half times greater than the flange thickness as before. The mount plate may be etched from full hard SST foil instead of stamped from quarter hard or soft SST foil. The harder mount plate material is desirable provides a stiffer platform from which to mount the load beam, but previous techniques, swaging, did not permit use of the harder material without adverse consequences to the shape of the mount plate and gram load stability. A harder mount plate is less likely to deform during attachment, or alternatively, can be made thinner for the same degree of deformation.
Preferably the invention mount plates are etched to shape. Etched construction achieves the lowest possible cost for the part. The etched construction also allows a degree of design freedom, such as a polygon shape to be used for the boss OD, which means the boss can be splined into the actuator arm hole.
The mount plate can have a boss such as a partially etched boss that is very short, approximately 0.003 inch. This boss is able to be much shorter than a stamped mounting plate boss because its primary function is to merely maintain alignment with (pilot into) the actuator tooling hole opening whereas in the prior art its function was the more difficult one of providing alignment.
In addition, in the prior art the boss necessarily had to have enough axial engagement to make the attachment of the mount plate to the actuator arm with sufficient force to successfully resist the applied torque found in use of the suspension.
In the present invention, a boss, if present at all, does not provide attachment engagement. In fact in many cases there is not even full circumferential contact between the mount plate boss and the actuator arm opening.
In place of the conventional swaged boss, the invention uses a relatively soft eyelet that has a terminal flange that is rolled or coined into axial engagement to effect attachment of the hard mount plate to the actuator arm.
The actuator arm performs the function of the washer that is usually used with an eyelet assembly. Thus, instead of making the whole suspension assembly mounting soft so it can be staked, the flange is hard and the eyelet is soft.
The cost of the mount plate drops from about 4 cents to less than two cents. The mount plate may be made with or without an etched boss for piloting. The mount plate may be obtained loose (as individual separate pieces), or on a strip with the same pitch as the load beam and flexure strips.
The eyelet is available at a less than a cent each, made of 300 series (non-magnetic) stainless steel, or brass, or other materials. Since the mounting plate flange or baseplate is not deformed in a swaging or staking operation in the course of assembling disk drive suspensions according to the invention, there is not the usual gram load change from this source.
Further, since the mounting plate baseplate is made of hard material, it is more rigid and flexes less in vibration.
The soft eyelet is crushed in suspension assembly by coining or rolling an unflanged end, the other end is generally preformed, pressing the, mount plate (carrying the load beam attached) and actuator arm tightly together, while maintaining the alignment of the mount plate and load beam. The deformation will be mostly on the eyelet because it is purposely made of softer stainless steel material than the load beam and mount plate stainless steel sheets.
The invention completely eliminates the staking process, and as well greatly improves the rigidity of the connection between mount plate and actuator. A better suspension and HGA performance is achieved.
In addition, in this invention, the load beam may on the slider side of the mount plate so that variations in gram load performance due to variations in actuator dimensions are be minimized.
This invention is ideal for one-head or two-head drives as shown in the ensuing description.
The foregoing benefits and advantages comprise the major objects of the invention and are realized in a disk drive suspension adapted to support a slider in operating proximity to a disk and for mounting to an actuator arm having a through opening, the suspension comprising a suspension assembly of a load beam having a base portion, a spring portion and a rigid portion, a mounting plate to which the load beam is attached by its the base portion, the mounting plate having a through opening registered with the actuator arm through opening, and a connector fastening the mounting plate and load beam to the actuator arm, the suspension assembly having first and second faces, the connector comprising an axially extended body of a length to extend through the mounting plate and actuator arm registered through openings and at least to the assembly first and second faces, the connector body having a first terminal flange axially engaging the first face of the suspension assembly and a second terminal flange axially engaging the second suspension assembly face in load beam to actuator mounting relation.
In this and like embodiments, typically, the plate and arm through openings have a circular perimeter and a given diameter, the connector body having a circular perimeter and a given diameter smaller than the plate and arm openings given diameter and such that the connector body circular perimeter does not radially engage the full extent of the plate and arm openings circular perimeters, the connector body first flange is preformed before assembling the load beam, mounting plate and actuator arm, the connector body second flange being formed in situ following assembly, the connector body second flange is formed by rolling the end of the connector body into a flange engaged with the assembly, the suspension assembly load beam is on the disk side of the assembly, the suspension assembly is paired with a second and like suspension assembly on the opposite side of the disk from the first suspension assembly, the mounting plate is planar, or the mounting plate is planar except for a boss defined by the mounting plate, the mounting plate boss being adapted to freely fit within the actuator through opening, the mounting plate defines a boss having a polygonal outer periphery, the actuator through opening has a polygonal inner periphery interfitting with the mounting plate boss outer periphery, the load beam defines a through opening registered with the mounting plate opening, the load beam being bonded to the mounting plate outwardly of the load beam through opening, the load beam is relieved circumferentially of the load beam through opening to have a recess sized to bodily receive one or another of the connector terminal flanges, and/or the suspension assembly load beam and mount plate are paired with a like suspension assembly load beam and mount plate, the suspension assemblies being arranged to provide sliders on opposite sides of the disk, the load beam bases and mount plates being mounted to and separated by a common actuator arm having the through opening, a single connector body extending through both the mount plate through openings and the actuator arm through opening with its the first and second flanges axially engaging first and second outer faces of the paired suspension assemblies.
In a preferred embodiment, the invention provides a disk drive suspension mounting plate comprising a flange having central tubular boss, the mounting plate boss having a polygonal outer periphery for engaging a complementary actuator arm opening.
In a further preferred embodiment, the invention provides a disk drive suspension for mounting on an actuator arm having a through opening, the suspension comprising a suspension assembly supporting a slider in operating proximity to a disk and comprising a load beam having a base portion, a spring portion and a rigid portion, a slider supported by the rigid portion, a mounting plate to which the load beam is attached by its the base portion, the mounting plate having a through opening registered with the actuator arm through opening, and a connector fastening the mounting plate and load beam to the actuator arm, the suspension assembly having first and second faces, the connector comprising an axially extended body of a length to extend through the mounting plate and actuator arm registered through openings and at least to the assembly first and second faces, the connector body having a first terminal flange axially engaging the first face of the suspension assembly and a second terminal flange axially engaging the second suspension assembly face in load beam to actuator mounting relation.
In this and like embodiments, typically, the plate and arm are metal structures, the plate and arm through openings having a circular perimeter and a given diameter, the connector body having a circular perimeter and a given diameter smaller than the plate and arm openings given diameter and such that the connector body circular perimeter does not radially engage the full extent of the plate and arm openings circular perimeters, the connector body first flange is preformed before assembling the load beam, mounting plate and actuator arm, the connector body second flange being formed in situ following assembly, the connector body second flange is formed by rolling the end of the connector body into a flange engaged with the assembly, the connector body second flange is rolled to have a radius, the load beam defines a through opening registered with the mounting plate opening, the load beam being bonded to the mounting plate outwardly of the load beam through opening, and the load beam is relieved circumferentially of the load beam through opening to have a recess sized to bodily receive one or another of the connector terminal flanges.
In a further embodiment the invention provides paired disk drive suspensions for mounting on a common actuator arm having a through opening, the suspensions each comprising a suspension assembly supporting a slider in operating proximity to opposite sides of a disk and comprising a load beam having a base portion, a spring portion and a rigid portion, a slider supported by the rigid portion, a mounting plate to which the load beam is attached by its the base portion, the mounting plate having a through opening registered with the actuator arm through opening and an outer face, and a single connector body extending through both the mount plate through openings and the actuator arm through opening, the single connector body having first and second flanges axially engaging the outer faces of the paired suspension assemblies.
In its method aspects the invention provides a method of assembling a disk drive suspension to an actuator arm having a through opening, including juxtaposing a through hole containing mount plate to which a load beam is attached with the actuator arm in through hole aligned relation, passing a connector having a first terminal flange through the aligned through holes, and forming a second terminal flange on the connector in situ in a manner forcing the mount plate and actuator arm together axially in load beam supporting relation on the actuator arm.